In a Power over Ethernet (PoE) system, Power Sourcing Equipment (PSE) provides inline power to one or more Powered Devices (PDs) through Ethernet cabling (e.g., CAT-5 cabling). Such inline power delivery eliminates the need for separate AC power wiring and its associated costs. Examples of PDs include Voice over IP (VoIP) telephones, Wireless Local Area Network (WLAN) transmitters, security cameras, and RFID readers.
A traditional 2-pair power transmission approach involves delivery of power through two twisted wire pairs of the Ethernet cabling to a PD. In accordance with IEEE 802.3af, the PD is able to draw a maximum of 12.95 W. In accordance with IEEE 802.3 at, the PD will be able to draw a 25.5 W. Both of these standards involve delivery of power to a PD through two twisted pairs of Ethernet cabling.
A 4-pair power delivery approach (4-pair mode) involves delivery of power to a PD through four twisted pairs of the Ethernet cabling carrying two power signals. That is, one power signal passes through two twisted wire pairs (as part of a first current loop) of the Ethernet cabling and separate power signal passes through two other twisted pairs (as part of a second current loop) of the Ethernet cabling.